OBJECTIVE To define the clinical role of laparoscopic Nissen fundoplication (LNF) in children with gastroesophageal reflux (GER), an appropriate understanding of its functional effects is required. The aim of this study was to investigate the motor function of the esophageal body and the lower esophageal sphincter (LES) with special reference to the effects of caloric nutrients in children undergoing LNF. METHODS Studies were performed in 12 children with GER (age, 6 months to 13 years) before and a month after LNF. Continuous manometric examination was performed with an infusion system using a sleeve sensor for an hour each before and after the administration of apple juice (AAJ; 10 mL/kg). RESULTS AAJ increased postoperative basal LES pressure from 15 +/- 7 to 20 +/- 6 mm Hg, whereas it decreased the preoperative values from 13 +/- 5 to 10 +/- 4 mm Hg (P < .05). Significant residual pressure was noted at the nadir of swallow-induced LES relaxation after LNF, which was increased by AAJ from 7 +/- 3 to 11 +/- 4 mm Hg. A child with a high nadir LES pressure showed postoperative dysphagia. Significant changes in the patterns of esophageal contractions were not noted after LNF. CONCLUSIONS Characteristics of the effect of LNF on the LES were a postprandial increase of basal LES pressure and significant residual LES pressure at the nadir of LES relaxation. The motor function of the esophageal body was not affected by LNF.